DESCRIPTION: The ras genes are activated by mutation in approximately 30% of human tumors and leukemias, and thus defining the role these genes play during tumor progression is of relevance clinically. The applicant's approach to studying ras action has been to identify genes that are regulated by the activated oncogene, and characterizing at the molecular level, the mechanisms of transcriptional regulation by ras. These studies have revealed that ras can regulate a diverse family of genes, including extracellular proteases such as urokinase plasminogen activator and stromeylsin that are thought to be cellular components necessary for the metastatic potential of tumors. These genes are stably expressed in ras transformed cells. This approach has resulted in the identification of members of the ets family of transcription as key nuclear components in mediating ras action. The expression of a dominant negative ets2 gene can abrogate ras transformation of cells as well as growth factor stimulated mitogenic growth. These observations demonstrate that effecting gene expression is a crucial aspect of ras initiated neoplastic transformation. More recent studies have implicated the genes ets1 and ets2 as the members of the ets-family that receive ras nuclear signals. Phosphorylation of a conserved amino acid domain appears necessary for the ras dependent activation of ets1 and ets2. Counterintuitively, mutation of the key residue that is phosphorylated in response to ras diminishes the ras dependent activity of ets1 and ets2, but also activates the oncogenic ability of the ets genes. These data lead to the proposal that ets1 and ets2 are bifunctional displaying both ras dependent and ras insensitive activities, that these activities are regulated by phosphorylation dependent interactions with distinct cellular proteins, and that upsetting the delicate balance between these two functions leads to cellular transformation. Experiments in this proposal are designed to test this hypothesis.